Will. Barlow dit que les eguilles de boussole sont beaucoup meilleures d'acier que de fer. Qu'apres estre tout a fait trempees dans de l'eau elles ne sont pas propres ni capables a recevoir la vertu magnetique mais qu'il faut les faire revenir a la couleur bleueGa naar voetnoot1).
L'armureGa naar voetnoot2) de fer est pourtant meilleure que celle d'acier trempè, et mesme que d'acier non trempè.
Gilbert que l'aimant se trouve avec la mine de fer. et que de l'aimant on tire du fer tres finGa naar voetnoot3).
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voetnoot6)
- ‘Tractatus siue Physiologia nova de magnete magneticisque corporibus et magno magnete tellure sex libris comprehensus à Guilielmo Gilberto Colcestrensi, medico Londinensi, etc.’ Excusus Sedini 1627 (ed. W. Lochmans; l'édition primitive est de 1600). Lib. I, Cap. XI: ‘Ferrum conflatum, non excitum magnete, ferrum trahit’.
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voetnoot7)
- Lib. I, Cap. XVI ‘Quod magnes et vena ferri idem sunt etc.’. Gilbert y dit e.a.: ‘Chimistarum aqua fortis eadem vulnera utrisque infligit’.
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voetnoot1)
- ‘Magneticall Aduertisements: or divers pertinent obseruations, and approved experiments concerning the nature and properties of the Loadstone: Very pleaseant for knowledge, and most needfull for practise, of travelling, or framing of Instruments fit for Trauellers both by Sea and Land’ [par William Barlowe], London, printed by E. Griffin for Timothy Barlow, 1616. Chap. X ‘Of the fashioning of the compasse needle’. L'auteur y dit: ‘The substance in any wise ought to bee pure steele, and not iron. For most assuredly steele will take at the least tenne times more vertue then iron can doe, but especially if it hath his right temper. And that is this: Heat it in the fire vntill it be past red hot, that it be whitish hot and quench it in cold water suddenly: So is it brickle in a manner as glasse it selfe, and is at that time incapable of the vertue of the Loadstone. Then must you, laying it vpon a plaine table, warily rubbe with fine sand all the blacke cullour from it, if before you put it into the fire, you annoynt it with soape, it will scale white of it selfe, then heat a barre of iron well neere red hot, and holding one end of the needle with a small paire of tongs, lay the other end vpon the hot barre, and presently you shall see that end turne from white to a yellowish, and after to a blewish cullour. then take that end with your tongs, and doe the like vnto the other, thrusting it forward upon the barre vntill the cullour of the whole needle become blewish: then throw it on a table, and let coole of it selfe: and so is he of the excellentest temper, and most capable to receive the greatest power from the
Magnet’.
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voetnoot2)
- Gilbert traite de l'aimant armé dans les Cap. XVII et suiv. du Lib. II de son ‘Tractatus’.
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voetnoot3)
- Cap. XVI du Lib. I, déjà cité dans la note 7 de la p. 565.
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Auteursrecht onbekend